S1 Exam 2nd

• Human sex cells


  Sperm and ovum (egg)
• Humans reproduce by sexual reproduction, involving the fusion of a male sex cell (sperm) and a female sex cell (ovum)
• Sperm


  • Has a head and a tail
  • Nucleus inside the head carries the genetic materials of the male parent
  • Tail enables the sperm to swim
• Ovum


  • Has a spherical shape
  • Much larger than a sperm
  • Surrounded by a jelly coat
  • Nucleus carries the genetic materials of the female parent
  • Cytoplasm contains food substances
  • Cannot move by itself
• Chromosomes in human sex cells

  Each sex cell has 23 chromosomes (one set of chromosomes)
• In females, each ovum contains 22 autosomes and one X chromosome
• In males, each sperm contain 22 autosomes, with half containing an X chromosome and half containing a Y chromosome
• Ovum has a food store, sperm does not
• In males, each body cell contains one X chromosome and one Y chromosome (XY)
• Male reproductive system


  • Sperms are produced in the testes
  • Sperms travel through the sperm ducts to the urethra
  • Sperms are mixed with fluid from sex glands to form semen
  • Semen is ejected from the penis during sexual intercourse
• Female reproductive system


  • Ova are produced in the ovaries
  • Ovum is released into the oviduct during ovulation
  • Ovum travels through the oviduct to the uterus
• The zygote formed after fertilization carries 46 chromosomes (two sets of chromosomes)
• Fertilization


  • Occurs when a sperm fuses with an ovum to form a zygote
  • Usually takes place in the oviduct of the female body
• The sperm and the ovum each carries 23 chromosomes
• Sperms


  • Swim towards the oviducts and fertilization takes place
• The sperm and the ovum each carries 23 chromosomes (one set of chromosomes)
• N


  One set of chromosomes
• When the sperm and the ovum fuse together during fertilization, the zygote formed with 46 chromosomes
• Fertilization


  1. Sperm fuses with an ovum to form a zygote

  2. Usually takes place in the oviduct of the female body
• The sperm and the ovum each carries 23 chromosomes. The zygote formed after fertilization carries 46 chromosomes
• The features each generation inherits from their parents are called traits
• DNA


  Carries genetic information
• The zygote formed after fertilization receives half of its genetic information from the father and half from the mother
• A always pairs with T, C always pairs with G
• Plural form of human sex cells

  • Male: Sperms
  • Female: Ova
• Implantation

  1. After fertilization, the zygote divides many times to form a ball of cells called an embryo

  2. The embryo is moved through the oviduct to the uterus

  3. The embryo then attaches to the uterine lining

  4. The woman is now pregnant
• Zygote

  The cell formed by the union of a sperm and an egg
• Embryo development

  1. Zygote is formed

  2. Zygote divides and develops into an embryo

  3. Embryo implants into the uterine lining
• Implantation


  The process in which the embryo attaches to the uterine lining